Lung cancer is the second most common cancer in both men and women and is the leading cause of cancer death for both sexes in industrialized countries. The disease is usually diagnosed at advanced stages resulting in an overall 5-year survival of only 18%. However, 5-year survival rate in patients with surgically resectable stage I non-small cell lung cancer (NSCLC) can be as high as 75%, consequently detecting early stage NSCLC may greatly reduce the mortality of this disease. Unfortunately, effective methods to provide an early diagnosis have not yet been established. Recent developments in molecular and epigenetic-based markers using patient serum may provide a less invasive and more robust approach for diagnosis of NSCLC at early, curable stages. Molecular markers can also improve risk stratification and prognosis assessment, which are important in the era of personalized medicine. Tumor cells have been shown to release miRNAs into the circulation in a highly stable, cell-free from in the blood. MiRNAs might be an ideal class of blood-based biomarkers for cancer detection. Our laboratory has reported that tissue miRNA profile is a strong predictor of poor survival in patients with squamous cell lung cancer (SCC) and adenocarcinoma (AC). We also found that DNA methylation of miRNA-34b/c is related to poor outcome in patients with lung ADC. Recently, we have discovered a specific 4- miRNA (miR-193b, miR-301, miR-141 and miR-200b) signature in the sera of patients with NSCLC that could be utilized for early detection of NSCLC. Therefore, we hypothesize that the presence of these miRNAs in sera from NSCLC patients can serve as non-invasive biomarkers for early diagnosis of lung cancer. We will test our hypothesis through the conduct of the following specific aims by three different cohorts of serum using RT- PCR: (1): one cohort from University of Michigan Medical School including 150 lung cancer and 100 non- cancer control sera. (2): second cohort prospectively collected due to indeterminate pulmonary nodules from a screening study at Vanderbilt University Medical Center including 88 lung cancer and 121 non-cancer controls (IPN). (3): third cohort including 150 sera from heavy smokers who are participating in a lung cancer screening program with low-dose CT (Computed Tomography) at Veterans Affairs Hospital Ann Arbor. The innovation of this study includes using a validated qRT-PCR based method to identify and quantify miRNAs directly from a large cohort of lung cancer sera, and developing miRNA-based biomarkers in patient sera for early lung cancer detection and further validation of this signature using both retrospective and prospective studies. This project has the potential to discover novel lung cancer diagnostic miRNAs that may improve early detection and therapy strategies for lung cancer which would have significant impact on reducing the high frequency of death seen in lung cancer.